#region Copyright & License

//
// Copyright 2001-2005 The Apache Software Foundation
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
//

#endregion

// .NET Compact Framework 1.0 has no support for Environment.GetEnvironmentVariable()
#if !NETCF

using System;
using System.IO;
using System.Security;

namespace log4net.Util.PatternStringConverters {
  /// <summary>
  /// Write an environment variable to the output
  /// </summary>
  /// <remarks>
  /// <para>
  /// Write an environment variable to the output writer.
  /// The value of the <see cref="log4net.Util.PatternConverter.Option"/> determines 
  /// the name of the variable to output.
  /// </para>
  /// </remarks>
  /// <author>Nicko Cadell</author>
  sealed class EnvironmentPatternConverter : PatternConverter {
    /// <summary>
    /// Write an environment variable to the output
    /// </summary>
    /// <param name="writer">the writer to write to</param>
    /// <param name="state">null, state is not set</param>
    /// <remarks>
    /// <para>
    /// Writes the environment variable to the output <paramref name="writer"/>.
    /// The name of the environment variable to output must be set
    /// using the <see cref="log4net.Util.PatternConverter.Option"/>
    /// property.
    /// </para>
    /// </remarks>
    protected override void Convert(TextWriter writer, object state) {
      try {
        if (Option != null && Option.Length > 0) {
          // Lookup the environment variable
          string envValue = Environment.GetEnvironmentVariable(Option);
          if (envValue != null && envValue.Length > 0)
            writer.Write(envValue);
        }
      } catch (SecurityException secEx) {
        // This security exception will occur if the caller does not have 
        // unrestricted environment permission. If this occurs the expansion 
        // will be skipped with the following warning message.
        LogLog.Debug(
          "EnvironmentPatternConverter: Security exception while trying to expand environment variables. Error Ignored. No Expansion.",
          secEx);
      } catch (Exception ex) {
        LogLog.Error("EnvironmentPatternConverter: Error occurred while converting environment variable.", ex);
      }
    }
  }
}

#endif // !NETCF